The use of cellulosic fibers in a range of consumer products is well known in the art. For example, cellulosic fibers can be used in paper products including bags, tags, toweling, tissue, map papers, paper patterns, napkins, poster papers, filter papers, and in many other grades or uses of paper. Cellulosic fibers are also utilized in structures or components of disposable absorbent products such as diaper liners, diaper wrap sheets, diaper absorbent structures, feminine napkin wrap sheets, disposable hospital bed pads, wipe materials, and the like.
Numerous chemical treatments for preparing cellulose fibers are also known in the art. For example, it is known that cellulose fibers may be treated with concentrated caustic solutions to alter the morphology of the fiber structure in a process referred to as “mercerization.” The mercerization process converts cellulose from its native form to a more thermodynamically stable form. Various caustic agents can be used as a mercerizing agent. Techniques for mercerization are described, for example, in Rydholm, ed. Pulping Processes (Interscience Publishers, 1965) and Ott, Spurlin and Grafflin, eds., Cellulose and Cellulose Derivatives, Vol. v, Part 1 (Interscience Publishers, 1954), the disclosures of which are incorporated by reference herein in their entireties.
Known processes for chemically treating cellulosic fibers typically disperse the cellulosic fibers in a diluent, such as an aqueous solution. However, it has been generally recognized that in order to ensure proper mixing of the cellulosic fibers and the treating chemicals as well as to ease the bulk transport of the treatment mixture, such known processes must have the cellulosic fibers present in the diluents at a low consistency. Such processes therefore generally result in the use of an excess of solvent in which the chemical treatment takes place, or the use of an excess of chemical treatment agent, thereby increasing the costs of manufacturing the chemically treated cellulosic fibers. Additionally, the use of sodium hydroxide, or other caustic agents, typically requires specialized handling procedures as well as recycling processes to ensure that such materials are not discharged to the environment. It is an object of the disclosed subject matter to provide cellulosic fibers which possess improved product properties.
U.S. Pat. No. 5,858,021 to Sun et al. describes a method for treating cellulosic fibers using an alkali metal hydroxide. Either concurrently with or subsequent to the treatment of the cellulosic fibers with an alkali metal hydroxide, the cellulose fibers can be treated with a high-energy refining process to achieve a desired amount of curl. Experimental values of wet curl using the disclosed methods vary between 0.266 and 0.325.
U.S. Pat. No. 6,896,810 to Ali et al. describes systems and methods for subjecting cellulosic fibers to alkaline treatment, which include equipment such as nanofiltration units and slurry concentrators that result in lowered consumption of alkaline solution during alkaline treatment.
U.S. Pat. No. 6,837,970 to Ko et al. describes a method of modifying a two-dimensional, flat fiber morphology of a never-been dried wood pulp into a three-dimensional twisted fiber morphology without the aid of a chemical cross-linker.